I-YaCy (ebizwa ngokuthi “ya see”) iyinjini yokusesha esabalalisiwe yamahhala, eyakhelwe kumigomo yamanethiwekhi amanethiwekhi ontanga-kuya-peer (P2P). Umnyombo wawo wuhlelo lwekhompiyutha olubhalwe ku-Java olusatshalaliswa kumakhulu amaningana amakhompyutha, kusukela ngo-September 2006, okuthiwa yi-YaCy-peers. I-YaCy-peer ngayinye igaqa ku-inthanethi ngokuzimela, ihlaziye futhi ikhombise amakhasi ewebhu, futhi igcine imiphumela yenkomba kusizindalwazi esivamile (esibizwa ngokuthi inkomba) esabelwa nabanye ontanga ye-YaCy kusetshenziswa izimiso zamanethiwekhi e-P2P. Kuyinjini yokusesha yamahhala wonke umuntu angayisebenzisa ukuze akhe ingosi yosesho ye-intranethi yabo kanye nokusiza ukusesha i-inthanethi yomphakathi ngokucacile.